import java.util.Scanner;

/**
 * @author zhaoqian
 * @create 2021/8/30 14:01
 */
public class Stringpaixu {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        while (in.hasNext()) {
            int str = in.nextInt();
            System.out.println(test(str));
        }
    }
    private static int test(int i) {
    if (i<3){
        return 1;
    }
        return test(i-2)+test(i-1);

    }

}
